235/70R16 vs 215/75R16
Going from one to the other changes the overall height by -0.9 %. That is inside the 3% band, so it fits and the speedometer stays close.
Side by side
| Measure | 235/70R16 | 215/75R16 | Change |
|---|---|---|---|
| Overall height | 29.0" | 28.7" | -0.9 % |
| Sidewall | 6.48" | 6.35" | -2.0 % |
| Section width | 235 mm | 215 mm | -8.5 % |
| Circumference | 91.0" | 90.2" | -0.9 % |
| Revs per mile | 697 | 703 | +0.9 % |
| Axle height | 14.48" | 14.35" | -3.3 mm |
| Approved rim width | 6.5–8.5" | 6–8" | overlap 6.5–8" |
Both are approved on a rim 6.5" to 8" wide. If yours is in that band, this is a tire change and nothing else.
What the speedometer will say
Calibrated for 235/70R16. Fit 215/75R16 and the needle stops telling the truth.
| Needle says | You are doing | Out by |
|---|---|---|
| 30 mph | 29.7 mph | -0.3 |
| 50 mph | 49.6 mph | -0.4 |
| 70 mph | 69.4 mph | -0.6 |
| 90 mph | 89.2 mph | -0.8 |
The odometer drifts with it. Ten thousand miles on the dial are really 9,912 on the road, so it over-counts by 88. At a true 70 mph the first turns 813 times a minute, the second 820.